1. Field of the Invention
This invention relates to a wrench with a quickly rotatable driving head.
2. Description of the Prior Art
As commonly known, a wrench is employed for screwing or unscrewing a thread locking member (not shown) such as a bolt, and quick-rotating ratchet wrenches have been developed for the convenience of operation. A conventional quick-rotating ratchet wrench, as shown in FIGS. 1, 2 and 3, includes a handle 10, a driving head 20 and a quick-disengaging unit 30 combined together. The handle 10 has one end provided with a bulging block 11 disposed with an insert hole 12 and having a circumferential side bored with a through hole 13 communicating with the insert hole 12 and provided with a first ratchet teeth 14. The driving head 20 is provided with a recessed groove 21 corresponding with the bulging block 11 and formed inside with an inner wall 21, which is provided with an annular recess 22 and second ratchet teeth 23. The quick-disengaging unit 30 has an operating member 31 provided to slide in the insert hole 12 and having both a shallow recess 311 and a deep recess 312 cut axially in a circumferential side A first spring 32 is fitted around the operating member 31 of the quick-disengaging unit 30, which is further provided with a restraining unit 33 received in the through hole 13 of the bulging block 11 and composed of two steel balls 331, 332 and a second spring 333 positioned between the two steel balls 331 and 332. In a normal condition, the two steel balls 331, 332 of the restraining unit 33 will respectively and elastically push against both the shallow recess 311 of the operating member 31 and the annular recess 22 of the driving head 20 to avoid the bulging block 11 of the handle 10 disengaging from the recessed groove 21 of the driving head 20 and hence, the handle 10 and the driving head 20 are impossible to rotate mutually because the first ratchet teeth 14 and the second ratchet teeth 23 tightly engage with each other. To enable the driving head 20 to rotate quickly relatively to the handle 10, referring to FIG. 3, only press down the operating member 31 to let the steel ball 331, which originally pushes against the shallow recess 311, changed to push against the deep recess 312, thus able to reduce the force that another steel ball 332 pushing against the annular recess 22. At this time, the handle 110 can easily be pulled upward and outward to disengage the first ratchet teeth 14 from the second ratchet teeth 23 and thus, the handle 10 can be operated to actuate the driving head 20 to rotate for 360 degrees for quickly screwing or unscrewing a thread locking member.
However, in the course of operating the driving head 20 to rotate quickly, restricted positioning between the bulging block 11 of the handle 10 and the recessed groove 21 of the driving head 20 is only effected by means of the steel ball 332 that pushes against the inner wall 211 of the recessed groove 21. Therefore, in an operating process, the bulging block 11 of the handle 10 is likely to cause disengagement in the recessed groove 21 of the driving head 20, resulting in a misgiving in safety of employing the conventional quickly-rotating ratchet wrench. In addition, the conventional quickly-rotating ratchet wrench using two steel balls for carrying out quick disengagement will add difficulty in production and assembly and increase cost, and the steel balls 331, 332 are liable to become deadlocked and especially, the second spring 333 may cause elastic fatigue after used for a long period.